Demonstrating effectiveness of online ads is a patchy affair.

The internet world needs to agree on a standard unit of measure.

It's encouraging to see i-level's campaign for EasyJet making it on to the shortlist for the IPA Advertising Effectiveness Awards. A first -- but hardly, you might think, a surprising first. If anyone can prove the effectiveness of an advertising campaign, it's a specialist agency working for an online advertiser. This, after all, is supposedly the most accountable medium ever invented.

In online, you can apply pure direct marketing models where the effectiveness sum is usually a pretty simple one -- response levels divided by media costs. And, sometimes, it's even more clear cut. When business plans are based on direct click-to-buy sales, the equation becomes revenue generated divided by media spend.

But we all know that things are not that simple. Take that oft-quoted legend that 90 per cent of online revenue still goes through ten or so websites. Not much evidence of thoughtful planning there, you might think.

And while we're at it, we could also point to last week's row over a low-price campaign click-through guarantee from Eyeconomy. Why would anyone want cheap clicks and nothing but cheap clicks? Surely the industry has moved beyond click-through as a useful measure of performance?

Is the industry really stuck at the starting gates when it comes to effectiveness? Is i-level's EasyJet campaign the exception? Charlie Dobres, the chief executive of i-level, admits standards in the industry are patchy: "Online should have a lot to teach other media but the truth is it still has a lot to learn. There are so many stories about what isn't happening in online but there's plenty of very positive stuff happening in pockets. There are two issues here -- understanding what the effectiveness issues really are in online and then being able to go out and do it. I think we're really starting to see both aspects of that taking off."

But it's advertisers, not agencies, who seem to be setting the pace here. Advertisers such as British Airways, for instance, that have a presence in the US market. Clive Peoples, BA's head of digital marketing, states: "We find we can get amazing accountability. The tools we ...